The Function of the Bank of England

1. It issues notes and coins. The Bank of England is the sole issuer of notes and coins in the UK. In theory you could take a £10 note to the Bank of England and ask for you equivalent sum of Gold. I don't know whether they would take kindly to such requests but in theory that is how they maintain confidence in notes and coins as a medium of exchange

2. Managing the government's debt. National Debt in the UK At the end of 2005/6 general government debt was £529.1 billion, equivalent to 42.1 per cent of GDP. [1]
To manage the government debt the bank of England sell bonds and gilts to the private sector. Usually bonds have a lifetime of about 30 years. In order to encourage people to buy government debt they need to offer an attractive interest rate. Interest payments on UK debt amount to nearly £30 billion a year